Rendering Error with OpenCL
I just made the render use 100% of my resolution [...].


This is an important change, since a higher rendering resolution requires more memory. The error you are getting tells you that Blender could not get enough memory from your graphics card.

If you do not want to use a lower resolution, simplify your scene by using lower resolution textures for far-away objects, using lower subdivition levels, fewer particles or in general less geometry when you can afford it.

Also have a look at the simplify tab in the scene settings:


Another possibility might be to render your image in parts, like shown here or in the answer to this question.